Agreed, when Sonic Mania came along I often heard “the first 2D Sonic game since 3+K” and thought that people were forgetting the advance series. You could tell they were crafted by a team that respected the feel of the games that came before and understood that Sonic was a solid platformer with speed as a reward gameplay mechanic. Not to mention it had a colour palette that never confused the main character from the background, something I think mania gets wrong from time to time.